Over recent years here has been an ever-increasing need for energy conservation in general lighting for residential, institutional and commercial buildings. One of the means for saving lighting energy has been the replacement of inefficient A-type incandescent lamps with tungsten/halogen lamps having about twice the L/P (lumens per Watt) or with CFL (Compact Fluorescent Lamps) having three times more lumens per Watt than A-type incandescent lamps.
In order to use tungsten/halogen lamps or CFL lamps in light fixtures that are recessed above a ceiling, UL (Underwriter's Laboratories) and various building codes require high-temperature ceramic lampholders, over 90% of which are for medium screw-base lamps. Then, in order to obtain a safety listing under UL standard1598 for a recessed light fixture, the fixture must have a thermal cut-off switch as well as the high-temperature ceramic lampholder. The purpose of the thermal switch is to prevent the lamp heat from burning the insulation off the wiring inside the fixture, which would create a possible electric shock hazard.